Hi
Here is a great site by the Canadian chap mentioned earlier who only fixes Turbo Actuators on the OM642 engine in Jeep WH/WK's.
http://turboactuatorrepair.com
He has a helpful Troubleshooting section on his site which takes you thru Symptoms & Diagnosis of suspect Turbo Actuators - he also give a Lifetime Guarantee on repairs. (Im not connected but he does seem to know what he is talking about & has good reviews).
Experience on my 2007 WH & also research on numerous MB & Jeep forums indicate that the 4 main OM642 Actuators (Swirl Motor/Turbo Actuator/EGR Valve/EGR Throttle Valve) all have plastic gearboxes/wheels & electronic components which are prone to failure in our high heat environment in OZ.
IMHO the actuators are a weak point in the overall engine design.
Perhaps OK in cool Europe but problematic in OZ.
Many of the DTC's thrown up by these actuators are intermittent making component diagnosis quite difficult.
Hang in there & stay safe. Cheers